1. Field of the Invention
The present invention relates to a double facer for use in a corrugated fiberboard sheet manufacturing system.
2. Description of the Related Art
A corrugated fiberboard sheet manufacturing system is made up of a single facer for forming a single faced corrugated fiberboard sheet by sticking a back linerboard and a wave-shaped corrugated medium together, and a double facer for forming a double faced corrugated fiberboard sheet by sticking the single faced corrugated fiberboard sheet and a front linerboard.
In the double facer, a single faced corrugated fiberboard sheet and an front linerboard, put in a superposed condition, are conveyed in a state placed between a heating means (for example, heating box) and a pressing means (for example, cylinder), thereby forming the aforesaid double faced corrugated fiberboard sheet.
A glue is applied previously onto flute tips of the single faced corrugated fiberboard sheet, and the single faced corrugated fiberboard sheet and the front linerboard are stuck to each other by the heating and pressing of the heating means and pressing means, thereby forming the double faced corrugated fiberboard sheet.
For reducing wrap or bonding failure of the double faced corrugated fiberboard sheet, there is a need to set the moisture content of the double faced corrugated fiberboard sheet at an appropriate value.
This moisture content varies with a pressing force of the aforesaid pressing means. This is because, as the pressing force of the pressing means increases, the double faced corrugated fiberboard sheet is more strongly pressed against the heating means to enhance the heating action to the double faced corrugated fiberboard sheet.
For this reason, in the conventional art, for optimizing the moisture content, an operator adjusts the pressing force of the pressing means manually in dependence upon his/her perception and experience. However, in fact, such a manual way encounters difficulty in promptly and appropriately setting a moisture content agreeing with fiberboard type, feed speed or the like, which can cause bonding failure or warp of a double faced corrugated fiberboard sheet which cannot be disregarded.